Thanks to Yota tech forum for tips on my recent Magnaflow muffler and 2.25" exhaust and K and N FILK purchase. My 1990 -4 runner has better low end response and and increase in the mid to high end as well. I have only 200 miles on these new changes and I haven't seen any increase in MPG.

Question #1: I read a thread about the computer needing over 500 miles to reset and then performance gains will improve. Is this true?

I also replaced my cap, rotor, fuel filter with Toyota parts, except for Bosch Platinum 4202 plugs. I notice a slight pinging in the mid range under acceleration. The ignition timing is set at 10 degrees.

Question #2: If the timing is stock at 10 degrees and I'm getting slight pinging in the midrange, does anyone think my plugs are to blame?

Question #3: Has anyone replaced the stock cat converter with a high flow cat ( car-sound) with positive results? I'm worried about a loss of back pressure which might effect low end performance.

Thanks for any replies....

 

1. You can pull the EFI fuse for a half hour or so. This will cause the computer to learn quicker.

2. Did you hook up the jumper wire between the two terminals before playing with the timing? A lot of guys run 12 degrees of timing without pinging. Perhaps you have a lot of carbon on top of your pistons and inside the cylinder head bowl. That creates hot spots and can cause pinging.

3. I think a couple of guys have tried high flow cats. If not mistaken the consensus was to keep the exhaust pipe at 2.25" or you'll lose a lot of bottom end power.

 

I just put on a whole new exhaust system. Header to free flow cat to Magnaflow muffler. Connected by 2.25" pipes. I would recommend the cat i have. It is 2.25" in and out. It flows more, but not TOO much more. All I have to say about the power is

 

Thanks for the reply,

1. I'll try the EFI fuse. I have to check the manual, but where is the EFI fuse? Is it near the diagnostic cover? A half an hour wait time seems a long time. I guess its a little different than rebooting a computer.

2. I did bypass the two connectors and the dash presented a flashing "check engine" light and O/D light. I used the dashboard tach to gauge the engine RPM's at 750-800. The timing was right on 10 degrees. With new Bosch Platinum 4202 plugs, I figured the motor would run perfect, but I still get a slight pinging around 65-70 while cruising. The top end seems to bog too. I wonder if the plugs are too hot and it is detonating at the higher temp range. I also found in the Chilton's manual that the timing can be "retarded" a few degrees to reduce the pinging.
Doesn't "retarding" the timing reduce performance and gas mileage?
I just had a "remanufactured" ATK motor put in. My original motor unfortunately and unexpectantly died a few years after the head gasket was replaced under the recall campaign.

3. I would like to replace the cat converter if I knew it was less restrictive than the stock one on my 1990. Is there any way to tell if a stock cat is still good?

Man, now I have opened up acan of worms...